Packing element

ABSTRACT

A packing element to be used in a reactor or mass transfer device wherein gas-gas, gas-liquid, and liquid-liquid phenomena are involved. The element is comprised of a housing having positioned therein adjacent the walls a first helical member of one hand, and a second helical member of opposite hand positioned within the first helical member.

United States Patent lnventor Allen 1i. Leybourne lll Decatur, Ala.Appl. No. 786.110 Filed Dec. 23, 1968 Patented June 29, 1971 AssigneeMonsantoCompany St. Lou's, Mo.

PACKING ELEMENT 7 Claims, 4 Drawing Figs.

US. Cl 261/79, 261/94, 23/284 Int. Cl B01f3/02, B01f3/04.B01f3/08 Fieldof Search 259/97,

[56] References Cited UNITED STATES PATENTS 906,555 12/1908 Pein 261/751,293,270 2/1919 Webbm. 261/95 2,761,657 9/1956 Rietz 259/97 PrimaryExaminerTim R. Miles Assistant Examiner-Steven H. Markowitz Atlorneys-Robert L. Broad, Jr. and Neal T. Willis PATENTEDJUNZQIQYI 3589,68?

FIG.3. FIG.4.

INVENTOR. A. E. L EYBOURNE m ATTORNEY PACKING ELEMENT BACKGROUND OF THEINVENTION 1. Field of the Invention This relates generally to packedcolumns and more specifically to elements which comprise the packingwithin such columns.

2. Description of the Prior Art Packed columns and their containedpacking have been known and used for some time. The contained packinghas assumed many structural shapes with corresponding advantages, all ofwhich have been balanced with effectiveness, economics, ease ofmaintaining, etc.

When dumped packing is considered the above-mentioned I factors alsocome into play with effectiveness being a major area of concern. Bydumped packing is meant the dumping of packing elements within a columnin a random manner as opposed to particularly positioning same withinthe column.

SUMMARY OF THE INVENTION It has now been found that by constructingpacking elements in the form of hollow cylinders, being housings, havingpositioned therein adjacent the walls a first helical member of one handand a second helical member of opposite hand positioned within thefirst, highly effective packing elements are produced which may be usedeither as dumped or particularly positioned packing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an elevation view showing apreferred embodiment of sections of helixes used in a packing elementaccording to this invention.

FIG. 2 is an elevation view, partially broken away, showing the packingelement of this invention.

FIG. 3 is a cross-sectional view taken substantially along lines 3-3 ofFIG. 1.

FIG. 4 is a cross-sectional view taken substantially along lines 4-4 ofFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with thisinvention, a packing element shown in FIG. 2 and generally denoted byreference numeral I is made up of a housing 2 which is preferably ahollow cylindrical member comprised of suitable material. Housing 2 hasdisposed therein adjacent its inner wall a left-handed helical member 3extending the lengththereof. Although it is not necessary for member 3to extend the length of housing 2, no useful purpose if visualized forhaving a partially empty housing. Within helical member 3 is disposed aright-handed helical member 4 which also extends the length of housing2. The labels as to hand are only for purposes of distinction withopposite hands being all that is required.

The difference between the inside diameter of first helical member 3 andthe outside diameter of second helical member 4 may be either positiveor negative as long as the material to be handled in the column can passthrough the packing element. FIG. 1 depicts one situation wherein thedifference is substantially zero.

The optimum shape of first helical member 3 is believed to be coiled andspringlike having a substantially triangular cross section as shown inFIG. 3. The optimum shape for a second helical member 4 is believed tobe the form ofa twisted ribbon having a substantially rectangular crosssection as shown in FIG. 41.

The term substantially triangular cross section is meant to include theembodiment shown in FIG. 3 wherein the two surfaces not adjacent thewalls of the housing are arcuate.

The cross section of first helical member 3 can also be round, square,etc., while the cross section of the second helical member 4 can varywidely and can even assume the shape ofa commercially obtained twistbit.

The theory behind the above-mentioned optimum shapes and the effect ofthe packing element in general is that the characteristic flow profilesof the material to be handled in a straight unobstructed duct remainsunchanged from one point to another along the path of transfer. This isparticularly true when viscous liquids are considered. Such liquidsstart against the walls of the duct and remain against the walls; therebeing nothing to change this situation.

When transfer of material through a helically shaped duct is considered,slippage occurs adjacent the walls. This helical flow path will lag thepath of the helical duct generating a pseudodisplacement and/or slippageof apparent contrary hand to that of the helical duct. This being thecase, and the, desire to be economical, means have been sought toprovide the same situation in packed columns and in particular, withinthe packing elements contained in the columns. The positioning of ahelical member adjacent the walls ofa hollow cylinder will solve some ofthe difficulties, but not all, because the material adjacent the helicalmember will intermingle and mix with itself. To effect mixing andintermingling with the material in the vicinity of the center of theduct, a second helical member of opposite hand can be positionedinterior of the first helical member.

To arrive at optimum shapes of the helical members, several factors haveto be taken into account. The helical transfers of material should be asclose together as possible for effective mixing and/or intermingling. Toprovide this, there must in essence be a duct with a rod through thecenter, concentric rod and duct, or duct having solid center in orderthat material flow will be maintained away from the center. Around thissolid center or rod, the distribution of the helical flows must beconsidered. Two separate flows of circular cross section would providelittle or no intermingling and mixing except that produced by anyturbulence that is present, whereas cooperating semicircular flows wouldprovide excellent mixing. The cross-sectional surfaces generated bycooperating semicircular helical flows would substantially assume theconfigurations shown in FIGS. 3 and 4.

The cooperation of the first and second helical members can beappreciated from viewing FIGS. 3 and 4, where in operation these membersare stationary and as the material enters the packing element, itexperiences tumbling, twisting, etc. and becomes intermingled and/ormixed with itself. This intermingling and mixing aids in keeping agreater quantity of material away from any one place, such as the walls,and aids in reducing undesirable results and insufficient surfacegeneration.

It is to be appreciated that a packing element according to thisinvention can be utilized and substituted for most any packing elementpresently available.

When substituted for presently available packing elements, not only aremost, if not all, of the advantages of the replaced elements retained,due to the exterior structure, but the added advantages present due tothe interior structure are also provided.

The foregoing illustrates the essential features of the invention aswell as some of the manners in which it may be practiced. Variouschanges and modifications may be made in practicing the inventionwithout departing from the spirit and scope thereof, and therefore, theinvention should not be limited except as defined in the appendedclaims.

Iclaim:

l. A packing element adapted for use in a packed column comprising ahousing having open ends, said housing having therein a first helicalmember of one hand, and a second helical member disposed within thefirst helical member and being of a hand opposite the hand of the firsthelical member, said helical members being stationary within saidhousing.

2. A packing element according to claim I wherein the shape of the firsthelical member is substantially that of a coil spring.

3. A packing element according to claim I wherein the shape of thesecond helical member is substantially that of a twisted ribbon.

hand disposed within the spring-shaped helical member, said helicalmember being stationary within said housing. 6. A packing elementaccording to claim 5 wherein the spring-shaped helical member has asubstantially triangular cross section.

7. A packing element according to claim 5 wherein the twistedribbon-shaped helical member has a substantially rectangular crosssection.

1. A packing element adapted for use in a packed column comprising ahousing having open ends, said housing having therein a first helicalmember of one hand, and a second helical member disposed within thefirst helical member and being of a hand opposite the hand of the firsthelical member, said helical members being stationary within saidhousing.
 2. A packing element according to claim 1 wherein the shape ofthe first helical member is substantially that of a coil spring.
 3. Apacking element according to claim 1 wherein the shape of the secondhelical member is substantially that of a twisted ribbon.
 4. A packingelement according to claim 1 wherein the outer periphery of the firsthelical member is positioned adjacent the inside wall of the housing. 5.A packing element adapted for use in a packed column comprising ahousing having open ends and having disposed therein: a. a spring-shapedhelical member of one hand, the outer periphery of which is positionedadjacent the inside wall of the housing, and b. a twisted ribbon-shapedhelical member of an opposite hand disposed within the spring-shapedhelical member, said helical member being stationary within saidhousing.
 6. A packing element according to claim 5 wherein thespring-shaped helical member has a substantially triangular crosssection.
 7. A packing element according to claim 5 wherein the twistedribbon-shaped helical member has a substantially rectangular crosssection.